Power converter

ABSTRACT

An object of the present invention is to provide a power converter capable of preventing upsizing of a chip on which a switching element is formed and detecting the temperature in a switching operation of the switching element. A power converter includes: an IGBT connected between an IGBT connected to the positive electrode side of a variable power supply and the negative electrode side of the variable power supply; a temperature detection resistor element connected to a gate to which a gate signal for controlling the switching operation of the IGBT is input and detecting the temperature of the IGBT; and a detector detecting the temperature level of the IGBT based on the voltage of the gate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2021-18163, filed on Feb. 8,2021, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a power converter including a switchingelement.

DESCRIPTION OF THE RELATED ART

PTL 1 discloses a gate drive circuit driving a switching element as asemiconductor element for power conversion. The gate drive circuitdisclosed in PTL 1 includes a temperature detection circuit detectingthe temperature of the switching element. PTL 2 discloses a MOSFEThaving a temperature sensing function.

CITATION LIST Patent Literatures

-   PTL 1: International Publication No. WO 2014/123046-   PTL 2: International Publication No. WO 2006/097896

SUMMARY OF THE INVENTION

The technology disclosed in PTL 1 requires an output terminal of thetemperature detection circuit arranged near the switching element.Therefore, the technology has a problem that the size of a chip on whichthe switching element is formed increases.

The technology disclosed in PTL 2 can detect the temperature in an offstate of the MOSFET. However, this technology has a problem that thetemperature in a switching operation of the MOSFET cannot be detected.

It is an object of the present invention to provide a power convertercapable of preventing upsizing of a chip on which a switching element isformed and detecting the temperature in a switching operation of theswitching element.

In order to achieve the above-described object, a power converteraccording to one aspect of the present invention includes: a secondswitching element connected between a first switching element connectedto a positive electrode side of a power supply and a negative electrodeside of the power supply; a temperature detection element connected to acontrol signal input terminal to which a control signal for controllinga switching operation of the second switching element is input andconfigured to detect the temperature of the second switching element;and a detection unit configured to detect the temperature level of thesecond switching element based on a voltage of the control signal inputterminal.

According to one aspect of the present invention, the upsizing of a chipon which the switching element is formed can be prevented and thetemperature in the switching operation of the switching element can bedetected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit block diagram illustrating an example of theschematic configuration of a power converter according to a firstembodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a temperature detectioncircuit provided in the power converter according to the firstembodiment of the present invention.

FIG. 3 is a diagram for explaining the temperature dependence of thecurrent-voltage characteristics of a switching element provided in thepower converter according to the first embodiment of the presentinvention.

FIG. 4 is a diagram illustrating a temperature detection circuitprovided in a power converter as Comparative Example 1.

FIG. 5 is a diagram illustrating a temperature detection circuitprovided in a power converter as Comparative Example 2.

FIG. 6 is a diagram illustrating an example of a temperature detectioncircuit provided in a power converter according to a second embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention illustrate devices and methods forembodying the technical idea of the present invention. The technicalidea of the present invention does not specify materials, shapes,structures, arrangement, and the like of constituent parts to thefollowing embodiments. The technical idea of the present invention canbe variously altered within the technical scope specified by Claims.

Hereinafter, an inverter device is described as an example of a powerconverter according to each embodiment, but the power converteraccording to these embodiments are not limited to the inverter deviceand is also applicable to a converter device, a modular multilevelconverter, and the like.

First Embodiment

(Overall Configuration of Power Converter)

A power converter according to a first embodiment of the presentinvention is described using FIG. 1 to FIG. 5 . First, an example of theoverall configuration of a power converter 1A according to thisembodiment is described using FIG. 1 .

As illustrated in FIG. 1 , the power converter 1A according to thisembodiment is connected to a variable power supply 4. The variable powersupply 4 has, for example, a three-phase AC power supply and a rectifiercircuit full-wave rectifying three-phase AC power input from thethree-phase AC power supply. The power converter 1A has a smoothingcapacitor 5 smoothing power rectified by the rectifier circuit. Althoughnot illustrated, the rectifier circuit is configured by full-bridgeconnecting six diodes or by full-bridge connecting six switchingelements.

A positive electrode side line Lp is connected to a positive electrodeside (i.e., a positive electrode output terminal of the rectifiercircuit) of the variable power supply 4. A negative electrode side lineLn is connected to a negative electrode side (i.e., a negative electrodeoutput terminal of the rectifier circuit) of the variable power supply4. The negative electrode side line Ln is connected to the negativeelectrode side of the variable power supply 4 via a resistor element R1provided in the power converter 1A. More specifically, one terminal ofthe resistor element R1 is connected to the negative electrode side lineLn and the other terminal of the resistor element R1 is connected to thenegative electrode side of the variable power supply 4. The smoothingcapacitor 5 is connected between the positive electrode side line Lp andthe negative electrode side line Ln. The power converter 1A includes aninverter device 2 converting a DC voltage applied between the positiveelectrode side line Lp and the negative electrode side line Ln into athree-phase (U-phase, V-phase, and W-phase) AC voltage and a controldevice 3 controlling the inverter device 2. The inverter device 2 isconfigured by, for example, an Intelligent Power Module (IPM).

The inverter device 2 has a main power supply input terminal Tp to whichthe positive electrode side line Lp is connected. The inverter device 2has a U-phase main power supply input terminal Tnu, a V-phase main powersupply input terminal Tnv, and a W-phase main power supply inputterminal Tnw connected to the negative electrode side line Ln. A U-phaseoutput terminal TU is a terminal from which a U-phase AC voltage isoutput, the U-phase AC voltage being generated by DC-AC converting a DCvoltage input from the variable power supply 4 by the inverter device 2.A V-phase output terminal TV is a terminal from which a V-phase ACvoltage is output, the V-phase AC voltage being generated by DC-ACconverting a DC voltage input from the variable power supply 4 by theinverter device 2. A W-phase output terminal TW is a terminal from whicha W-phase AC voltage is output, the W-phase AC voltage being generatedby DC-AC converting a DC voltage input from the variable power supply 4by the inverter device 2.

As illustrated in FIG. 1 , the inverter device 2 provided in the powerconverter 1A has insulated gate bipolar transistors 201 (one example ofthe first switching element) connected to the positive electrode side ofthe variable power supply (one example of the power supply) 4. Theinverter device 2 has insulated gate bipolar transistors 211 (oneexample of the second switching element) connected between the insulatedgate bipolar transistors 201 and the negative electrode side of thevariable power supply 4. Hereinafter, the insulated gate bipolartransistor is abbreviated as “IGBT”. In this embodiment, the firstswitching element is the IGBT 201 having a gate G as a control signalinput terminal and the second switching element is the IGBT 211 having agate G as a control signal input terminal.

The inverter device 2 has temperature detection resistor elements (oneexample of the temperature detection element) 213 connected to the gatesG (one example of the control signal input terminal) to which gatesignals SgUL, SgVL, SgWL (examples of the control signal, details aredescribed later) for controlling switching operations of the IGBTs 211are input and detecting the temperatures of the IGBTs 211. In thisembodiment, the temperature detection element is a resistor elementhaving one terminal connected to the gate G of the IGBT 211 and theother terminal connected to an emitter E of the IGBT 211. Thiseliminates the necessity of providing a terminal for connecting oneterminal and the other terminal of the temperature detection resistorelement 213 to a gate drive circuit 23 (details are described later) ineach of semiconductor elements 21 u, 21 v, 21 w. Therefore, thesemiconductor elements 21 u, 21 v, 21 w can be downsized. The inverterdevice 2 has a U-phase detection unit 234U, a V-phase detection unit234V, and a W-phase detection unit 234W (examples of the detection unit,not illustrated in FIG. 1 , see FIG. 2 ) each detecting the temperaturelevel of the IGBT 211 based on the voltage of the gate G.

As illustrated in FIG. 1 , the inverter device 2 has semiconductorelements 20 u, 20 v, 20 w each having the IGBT 201 as avoltage-controlled semiconductor element, for example, constituting anupper arm portion connected to the positive electrode side line Lp. Theinverter device 2 further has the semiconductor elements 21 u, 21 v, 21w each having the IGBT 211 constituting a lower arm portion connected tothe negative electrode side line Ln.

The IGBT 201 provided in the semiconductor element 20 u and the IGBT 211provided in the semiconductor element 21 v are connected in seriesbetween the positive electrode side line Lp and the negative electrodeside line Ln to constitute a U-phase output arm 2U. The IGBT 201provided in the semiconductor element 20 v and the IGBT 211 provided inthe semiconductor element 21 v are connected in series between thepositive electrode side line Lp and the negative electrode side line Lnto constitute a V-phase output arm 2V. The IGBT 201 provided in thesemiconductor element 20 w and the IGBT 211 provided in thesemiconductor element 21 w are connected in series between the positiveelectrode side line Lp and the negative electrode side line Ln toconstitute a W-phase output arm 2W.

A reflux diode 202 is connected in anti-parallel to the IGBT 201provided in each of the semiconductor elements 20 u, 20 v, 20 w. TheIGBT 201 and the reflux diode 202 provided in the semiconductor element20 u are formed on the same semiconductor chip. The IGBT 201 and thereflux diode 202 provided in the semiconductor element 20 v are formedon the same semiconductor chip. The IGBT 201 and the reflux diode 202provided in the semiconductor element 20 w are formed on the samesemiconductor chip. The IGBT 201 and the reflux diode 202 provided ineach of the semiconductor elements 20 u, 20 v, 20 w are formed ondifferent semiconductor chips.

The semiconductor elements 20 u, 20 v, 20 w each have a gate terminal Tgconnected to the gate G of the IGBT 201, a collector terminal Tcconnected to a collector C of the IGBT 201, and an emitter terminal Teconnected to the emitter E of the IGBT 201. A cathode of the refluxdiode 202 is connected to the collector terminal Tc. An anode of thereflux diode 202 is connected to the emitter terminal Te. The collectorterminal Tc of each of the semiconductor elements 20 u, 20 v, 20 w isconnected to the main power supply input terminal Tp provided in theinverter device 2. Therefore, the collector C of the IGBT 201 and thecathode of the reflux diode 202 provided in each of the semiconductorelements 20 u, 20 v, 20 w are connected to the main power supply inputterminal Tp.

A reflux diode 212 is connected in anti-parallel to the IGBT 211provided in each of the semiconductor elements 21 u, 21 v, 21 w. Thesemiconductor elements 21 u, 21 v, 21 w each have a temperaturedetection resistor element 213 connected between the gate G and theemitter E of the IGBT 211.

The reflux diode 212, the IGBT 211, and the temperature detectionresistor element 213 provided in the semiconductor element 21 u areformed on the same semiconductor chip. The reflux diode 212, the IGBT211, and the temperature detection resistor element 213 provided in thesemiconductor element 21 v are formed on the same semiconductor chip.The reflux diode 212, the IGBT 211, and the temperature detectionresistor element 213 provided in the semiconductor element 21 w areformed on the same semiconductor chip. The reflux diode 212, the IGBT211, and the temperature detection resistor element 213 provided in eachof the semiconductor elements 21 u, 21 v, 21 w are formed on differentsemiconductor chips. As described above, the formation of the IGBT 211,the temperature detection resistor element 213, and the reflux diode 212on the same semiconductor chip enables the downsizing of the inverterdevice 2.

The semiconductor elements 21 u, 21 v, 21 w each have a gate terminal Tgconnected to the gate G of the IGBT 211, a collector terminal Tcconnected to the collector C of the IGBT 211, and an emitter terminal Teconnected to the emitter E of the IGBT 211. A cathode of the refluxdiode 212 is connected to the collector terminal Tc. An anode of thereflux diode 212 is connected to the emitter terminal Te. One terminalof the temperature detection resistor element 213 is connected to thegate G and the gate terminal Tg of the IGBT 211. The other terminal ofthe temperature detection resistor element 213 is connected to theemitter E of the IGBT 211 and the cathode of the reflux diode 212 andthe emitter terminal Te.

The emitter terminal Te of the semiconductor element 21 u is connectedto the U-phase main power supply input terminal Tnu provided in theinverter device 2. Therefore, the emitter E of the IGBT 211, the anodeof the reflux diode 212, and the other terminal of the temperaturedetection resistor element 213 provided in the semiconductor element 21u are connected to the U-phase main power supply input terminal Tnu. Theemitter terminal Te of the semiconductor element 21 v is connected tothe V-phase main power supply input terminal Tnv provided in theinverter device 2. Therefore, the emitter E of the IGBT 211, the anodeof the reflux diode 212, and the other terminal of the temperaturedetection resistor element 213 provided in the semiconductor element 21v are connected to the V-phase main power supply input terminal Tnv. Theemitter terminal Te of the semiconductor element 21 w is connected tothe W-phase main power supply input terminal Tnw provided in theinverter device 2. Therefore, the emitter E of the IGBT 211, the anodeof the reflux diode 212, and the other terminal of the temperaturedetection resistor element 213 provided in the semiconductor element 21w are connected to the W-phase main power supply input terminal Tnw.

The emitter terminal Te of the semiconductor element 20 u and thecollector terminal Tc of the semiconductor element 21 u are connected toeach other and each are connected to the U-phase output terminal TU. Theemitter terminal Te of the semiconductor element 20 v and the collectorterminal Tc of the semiconductor element 21 v are connected to eachother and each are connected to the V-phase output terminal TV. Theemitter terminal Te of the semiconductor element 20 w and the collectorterminal Tc of the semiconductor element 21 w are connected to eachother and each are connected to the W-phase output terminal TW.

As illustrated in FIG. 1 , a motor 7, for example, which serves as aload is connected to the U-phase output terminal TU, the V-phase outputterminal TV, and the W-phase output terminal TW provided in the inverterdevice 2. Therefore, the emitter E of the IGBT 201 provided in each ofthe semiconductor elements 20 u, 20 v, 20 w and the collector C of theIGBT 211 provided in each of the semiconductor elements 21 u, 21 v, 21 ware connected to the motor 7.

The inverter device 2 is controlled by the control device 3 to performswitching operations of the IGBT 201 provided in each of thesemiconductor elements 20 u, 20 v, 20 w and the IGBT 211 provided ineach of the semiconductor elements 21 u, 21 v, 21 w. Thus, the inverterdevice 2 converts a DC voltage on the positive electrode side of thevariable power supply 4 input from the main power supply input terminalTp and DC voltages on the negative electrode side of the variable powersupply 4 input from the U-phase main power supply input terminal Tnu,the V-phase main power supply input terminal Tnv, and the W-phase mainpower supply input terminal Tnw into an AC voltage to generate athree-phase AC voltage. The inverter device 2 outputs the U-phase ACvoltage of the generated three-phase AC voltage to the motor 7 from theU-phase output terminal TU. The inverter device 2 outputs the V-phase ACvoltage of the generated three-phase AC voltage to the motor 7 from theV-phase output terminal TV. The inverter device 2 outputs the W-phase ACvoltage of the generated three-phase AC voltage to the motor 7 from theW-phase output terminal TW. Thus, the inverter device 2 can supply thethree-phase AC power to the motor 7.

As illustrated in FIG. 1 , the inverter device 2 has a signal inputterminal Tiuh to which an input signal SinUH output by the controldevice 3 is input, an input signal input terminal Tivh to which an inputsignal SinVH output by the control device 3 is input, and a signal inputterminal Tiwh to which an input signal SinWH output by the controldevice 3 is input. The inverter device 2 has a signal input terminalTiul to which an input signal SinUL output by the control device 3 isinput, a signal input terminal Tivl to which an input signal SinVLoutput by the control device 3 is input, and a signal input terminalTiwl to which an input signal SinWL output by the control device 3 isinput. The input signals SinUH, SinVH, SinWH are used to generate gatesignals SgUH, SgVH, SgWH for driving the semiconductor elements 20 u, 20v, 20 w, respectively. The input signals SinUL, SinVL, SinWL are used togenerate the gate signals SgUL, SgVL, SgWL for driving the semiconductorelements 21 u, 21 v, 21 w, respectively.

As illustrated in FIG. 1 , the power converter 1A includes a gate drivecircuit 22 outputting the gate signals SgUH, SgVH, SgWH to the gate G ofthe IGBT 201 provided in each of the semiconductor elements 20 u, 20 v,20 w, respectively, and driving the IGBT 201. The power converter 1Afurther includes the gate drive circuit 23 (one example of the drivecircuit) outputting the gate signals SgUL, SgVL, SgWL to the gate G ofthe IGBT 211 provided in each of the semiconductor elements 21 u, 21 v,21 w, respectively, and driving the IGBT 211. The gate drive circuits22, 23 are provided in the inverter device 2. The gate drive circuit 22individually controls the switching operations of the IGBTs 201 providedin the semiconductor elements 20 u, 20 v, 20 w. The gate drive circuit23 individually controls the switching operations of the IGBTs 211provided in the semiconductor elements 21 u, 21 v, 21 w.

The gate drive circuit 22 has an input terminal Tiu which is connectedto the signal input terminal Tiuh and to which the input signal SinUH isinput, an input terminal Tiv which is connected to the signal inputterminal Tivh and to which the input signal SinVH is input, and an inputterminal Tiw which is connected to the signal input terminal Tiwh and towhich the input signal SinWH is input.

The gate drive circuit 22 has an output terminal Tou connected to thegate terminal Tg of the semiconductor element 20 u. Although a detaileddescription is omitted, the gate drive circuit 22 outputs the gatesignal SgUH switching on (conduction state) the IGBT 201 provided in thesemiconductor element 20 u from the output terminal Tou when the voltagelevel of the input signal SinUH input from the input terminal Tiu islow. On the other hand, the gate drive circuit 22 outputs the gatesignal SgUH switching off (non-conduction state) the IGBT 201 providedin the semiconductor element 20 u from the output terminal Tou when thevoltage level of the input signal SinUH input from the input terminalTiu is high. As described above, the gate drive circuit 22 outputs thegate signal SgUH for controlling the switching operation of the IGBT 201provided in the semiconductor element 20 u from the output terminal Tou.

The gate drive circuit 22 has an output terminal Tov connected to thegate terminal Tg of the semiconductor element 20 v. Although a detaileddescription is omitted, the gate drive circuit 22 outputs the gatesignal SgVH switching on (conduction state) the IGBT 201 provided in thesemiconductor element 20 v from the output terminal Tov when the voltagelevel of the input signal SinVH input from the input terminal Tiv islow. On the other hand, the gate drive circuit 22 outputs the gatesignal SgVH switching off (non-conduction state) the IGBT 201 providedin the semiconductor element 20 v from the output terminal Tov when thevoltage level of the input signal SinVH input from the input terminalTiv is high. As described above, the gate drive circuit 22 outputs thegate signal SgVH for controlling the switching operation of the IGBT 201provided in the semiconductor element 20 v from the output terminal Tov.

The gate drive circuit 22 has an output terminal Tow connected to thegate terminal Tg of the semiconductor element 20 w. Although a detaileddescription is omitted, the gate drive circuit 22 outputs the gatesignal SgWH switching on (conduction state) the IGBT 201 provided in thesemiconductor element 20 w from the output terminal Tow when the voltagelevel of the input signal SinWH input from the input terminal Tiw islow. On the other hand, the gate drive circuit 22 outputs the gatesignal SgWH switching off (non-conduction state) the IGBT 201 providedin the semiconductor element 20 w from the output terminal Tow when thevoltage level of the input signal SinWH input from the input terminalTiw is high. As described above, the gate drive circuit 22 outputs thegate signal SgWH for controlling the switching operation of the IGBT 201provided in the semiconductor element 20 w from the output terminal Tow.

As illustrated in FIG. 1 , the gate drive circuit 22 has a power supplyterminal Tcc to which a control power supply voltage VccH (voltage valueof 15 V, for example) is input, the control power supply voltage VccHserving as a power supply of, for example, a circuit (not illustrated)generating the gate signals SgUH, SgVH, SgWH. The gate drive circuit 22further has a power supply terminal Tdu to which a drive power supplyvoltage is input, the drive power supply voltage serving as a powersupply of a driver circuit (not illustrated) provided in the circuit anddriving the IGBT 201 of the semiconductor element 20 u.

The gate drive circuit 22 has a low potential terminal Tsu connected tothe U-phase output terminal TU provided in the inverter device 2. Thelow potential terminal Tsu is connected to the emitter terminal Te ofthe semiconductor element 20 u. The low potential terminal Tsu isconnected to the emitter E of the IGBT 201 and the anode of the refluxdiode 202 provided in the semiconductor element 20 u via the emitterterminal Te of the semiconductor element 20 u. Thus, the potential onthe negative electrode side of the driver circuit (not illustrated)driving the IGBT 201 provided in the semiconductor element 20 u is equalto the potential on the low potential side (emitter E in thisembodiment) of the IGBT 201 provided in the semiconductor element 20 uvia the low potential terminal Tsu and the emitter terminal Te of thesemiconductor element 20 u.

The gate drive circuit 22 has a low potential terminal Tsv connected tothe V-phase output terminal TV provided in the inverter device 2. Thelow potential terminal Tsv is connected to the emitter terminal Te ofthe semiconductor element 20 v. The low potential terminal Tsv isconnected to the emitter E of the IGBT 201 and the anode of the refluxdiode 202 provided in the semiconductor element 20 v via the emitterterminal Te of the semiconductor element 20 v. Thus, the potential onthe negative electrode side of a driver circuit (not illustrated)driving the IGBT 201 provided in the semiconductor element 20 v is equalto the potential on the low potential side (emitter E in thisembodiment) of the IGBT 201 provided in the semiconductor element 20 vvia the low potential terminal Tsv and the emitter terminal Te of thesemiconductor element 20 v.

The gate drive circuit 22 has a low potential terminal Tsw connected tothe W-phase output terminal TW provided in the inverter device 2. Thelow potential terminal Tsw is connected to the emitter terminal Te ofthe semiconductor element 20 w. The low potential terminal Tsw isconnected to the emitter E of the IGBT 201 and the anode of the refluxdiode 202 provided in the semiconductor element 20 w via the emitterterminal Te of the semiconductor element 20 w. Thus, the potential onthe negative electrode side of a driver circuit (not illustrated)driving the IGBT 201 provided in the semiconductor element 20 w is equalto the potential on the low potential side (emitter E in thisembodiment) of the IGBT 201 provided in the semiconductor element 20 wvia the low potential terminal Tsw and the emitter terminal Te of thesemiconductor element 20 w.

The inverter device 2 has a U-phase power supply terminal TBu to which adrive power supply voltage is input, the drive power supply voltageserving as a power supply of the driver circuit (not illustrated)driving the IGBT 201 provided in the semiconductor element 20 u, and acontrol power supply terminal TccH to which the control power supplyvoltage VccH is input. The U-phase power supply terminal TBu isconnected to the power supply terminal Tdu of the gate drive circuit 22.The control power supply terminal TccH is connected to the power supplyterminal Tcc of the gate drive circuit 22.

The power converter 1A has a capacitor Cu connected between the U-phasepower supply terminal TBu and the U-phase output terminal TU provided inthe inverter device 2. One electrode of the capacitor Cu is connected tothe U-phase power supply terminal TBu and the other electrode of thecapacitor Cu is connected to the U-phase output terminal TU. Theinverter device 2 has a resistor element R3 and a diode D connected inseries between the power supply terminal Tcc and the power supplyterminal Tdu. One terminal of the resistor element R3 is connected tothe power supply terminal Tcc and the control power supply terminal TccHand the other terminal of the resistor element R3 is connected to ananode of the diode D. A cathode of the diode D is connected to the powersupply terminal Tdu and the U-phase power supply terminal TBu. The diodeD and the capacitor Cu constitute a bootstrap circuit. The bootstrapcircuit can apply a voltage, which is obtained by adding a voltage onthe positive electrode side of the variable power supply 4 to thecontrol power supply voltage VccH, to the power supply terminal Tdu ofthe gate drive circuit 22. Thus, the gate drive circuit 22 can set thepower supply of the driver circuit driving the IGBT 201 provided in thesemiconductor element 20 u to be higher than a voltage applied to thecollector C of the IGBT 201.

Although not illustrated, the gate drive circuit 22 has a power supplyterminal to which a drive power supply voltage is input, the drive powersupply voltage serving as a power supply of a driver circuit (notillustrated) driving the IGBT 201 provided in each of the semiconductorelements 20 v, 20 w. Thus, the gate drive circuit 22 can set the powersupply of the driver circuit driving the IGBT 201 provided in thesemiconductor element 20 v to be higher than a voltage applied to thecollector C of the IGBT 201. Similarly, the gate drive circuit 22 canset the power supply of the driver circuit driving the IGBT 201 providedin the semiconductor element 20 w to be higher than a voltage applied tothe collector C of the IGBT 201.

The gate drive circuit 22 has a reference potential terminal Tgnd. Thereference potential terminal Tgnd provided in the gate drive circuit 22is a terminal for inputting a potential serving as the reference for theoperation of, for example, the circuit generating the gate signals SgUH,SgVH, SgWH for controlling the switching operation of the IGBT 201provided in each of the semiconductor elements 20 u, 20 v, 20 w,respectively. The reference potential terminal Tgnd of the gate drivecircuit 22 is connected to a common reference potential terminal Tcomprovided in the inverter device 2.

As illustrated in FIG. 1 , the gate drive circuit 23 has a referencepotential terminal Tgnd. The reference potential terminal Tgnd providedin the gate drive circuit 23 is a terminal for inputting a potentialserving as the reference for the operation of, for example, the circuitgenerating the gate signals SgUL, SgVL, SgWL for controlling theswitching operation of the IGBT 211 provided in each of thesemiconductor elements 21 u, 21 v, 21 w, respectively. The referencepotential terminal Tgnd of the gate drive circuit 23 is connected to thecommon reference potential terminal Tcom provided in the inverter device2. The reference potential terminal Tgnd of the gate drive circuit 23and the reference potential terminal Tgnd of the gate drive circuit 22are connected to each other via the common reference potential terminalTcom. The common reference potential terminal Tcom is connected (forexample, grounded) to the reference plane of the potential in the powerconverter 1A.

The gate drive circuit 23 has an input terminal Tiu which is connectedto a signal input terminal Tiul and to which an input signal SinULoutput by the control device 3 is input, an input terminal Tiv which isconnected to a signal input terminal Tivl and to which an input signalSinVL output by the control device 3 is input, and an input terminal Tiwwhich is connected to a signal input terminal Tiwl and to which an inputsignal SinWL output by the control device 3 is input.

The gate drive circuit 23 has an output terminal Tou connected to thegate terminal Tg of the semiconductor element 21 u. Although details aredescribed later, the gate drive circuit 23 outputs a gate signal SgULswitching on (conduction state) the IGBT 211 provided in thesemiconductor element 21 u from the output terminal Tou when the voltagelevel of the input signal SinUL input from the input terminal Tiu islow. On the other hand, the gate drive circuit 23 outputs the gatesignal SgUL switching off (non-conduction state) the IGBT 211 providedin the semiconductor element 21 u from the output terminal Tou when thevoltage level of the input signal SinUL input from the input terminalTiu is high. As described above, the gate drive circuit 23 outputs thegate signal SgUL for controlling the switching operation of the IGBT 211provided in the semiconductor element 21 u from the output terminal Tou.

The gate drive circuit 23 has an output terminal Toy connected to thegate terminal Tg of the semiconductor element 21 v. Although details aredescribed later, the gate drive circuit 23 outputs the gate signal SgVLswitching on (conduction state) the IGBT 211 provided in thesemiconductor element 21 v from the output terminal Toy when the voltagelevel of the input signal SinVL input from the input terminal Tiv islow. On the other hand, the gate drive circuit 23 outputs the gatesignal SgVL switching off (non-conduction state) the IGBT 211 providedin the semiconductor element 21 v from the output terminal Tov when thevoltage level of the input signal SinVL input from the input terminalTiv is high. As described above, the gate drive circuit 23 outputs thegate signal SgVL for controlling the switching operation of the IGBT 211provided in the semiconductor element 21 v from the output terminal Tov.

The gate drive circuit 23 has an output terminal Tow connected to thegate terminal Tg of the semiconductor element 21 w. Although a detaileddescription is omitted, the gate drive circuit 23 outputs the gatesignal SgWL switching on (conduction state) the IGBT 211 provided in thesemiconductor element 21 w from the output terminal Tow when the voltagelevel of the input signal SinWL input from the input terminal Tiw islow. On the other hand, the gate drive circuit 23 outputs the gatesignal SgWL switching off (non-conduction state) the IGBT 211 providedin the semiconductor element 21 w from the output terminal Tow when thevoltage level of the input signal SinWL input from the input terminalTiw is high. As described above, the gate drive circuit 23 outputs thegate signal SgWL for controlling the switching operation of the IGBT 211provided in the semiconductor element 21 w from the output terminal Tow.

The gate terminal Tg of the semiconductor element 21 u to which the gatesignal SgUL is input and which is connected to the gate G of the IGBT211 provided in the semiconductor element 21 u is equivalent to thecontrol signal input terminal. The gate terminal Tg of the semiconductorelement 21 v to which the gate signal SgVL is input and which isconnected to the gate G of the IGBT 211 provided in the semiconductorelement 21 v is equivalent to the control signal input terminal. Thegate terminal Tg of the semiconductor element 21 w to which the gatesignal SgWL is input and which is connected to the gate G of the IGBT211 provided in the semiconductor element 21 w is equivalent to thecontrol signal input terminal.

As illustrated in FIG. 1 , the gate drive circuit 23 has a power supplyterminal Tcc to which a power supply of, for example, a circuit (notillustrated) generating the gate signals SgUL, SgVL, SgWL is input. Thepower supply terminal Tcc of the gate drive circuit 23 is connected to acontrol power supply terminal TccL provided in the inverter device 2. Tothe control power supply terminal TccL, the control power supply voltageVccH (voltage value of 15 V, for example) is input. Therefore, thecontrol power supply voltage VccH is input as the power supply of, forexample, the circuit (not illustrated) generating the gate signals SgUL,SgVL, SgWL to the gate drive circuit 23 via the control power supplyterminal TccL and the power supply terminal Tcc.

As illustrated in FIG. 1 , the gate drive circuit 23 has a detectionsignal output terminal Ttp from which a temperature detection signalStemp based on the temperature levels of the IGBTs 211 detected by theU-phase detection unit 234U, the V-phase detection unit 234V, and theW-phase detection unit 234W (not illustrated in FIG. 1 , see FIG. 2 ) isoutput. The inverter device 2 has a temperature output terminal Ttempconnected to the detection signal output terminal Ttp and the controldevice 3. This enables the inverter device 2 to output the temperaturedetection signal Stemp output from the detection signal output terminalTtp of the gate drive circuit 23 to the control device 3 from thetemperature output terminal Ttemp.

As illustrated in FIG. 1 , the inverter device 2 has an overcurrentdetection input terminal TIS. The overcurrent detection input terminalTIS is connected to the detection terminal Ts provided in the gate drivecircuit 23 and one terminal of a resistor element R2 provided in thepower converter 1A. The other terminal of the resistor element R2 isconnected to one terminal of the resistor element R1 and the U-phasemain power supply input terminal Tnu, the V-phase main power supplyinput terminal Tnv, and the W-phase main power supply input terminal Tnwprovided in the inverter device 2.

Although not illustrated, the gate drive circuit 23 has an overcurrentprotective circuit. The overcurrent protective circuit performs controlto switch off the IGBT 211 when a current output from at least one ofthe U-phase main power supply input terminal Tnu, the V-phase main powersupply input terminal Tnv, and the W-phase main power supply inputterminal Tnw (i.e. a current flowing to the IGBT 211) has a currentamount larger than a predetermined current amount and when a voltageinput from the overcurrent detection input terminal TIS and thedetection terminal Ts has a value larger than a predetermined value.This enables the gate drive circuit 23 to stop the flow of anovercurrent to at least one of the IGBTs 211 provided in thesemiconductor elements 21 u, 21 v, 21 w and prevent damage to the IGBT211.

As illustrated in FIG. 1 , the power converter 1A includes a constantvoltage source 6 connected to the negative electrode side of thevariable power supply 4 and the other terminal of the resistor elementR1. The positive electrode side of the constant voltage source 6 isconnected to the negative electrode side of the variable power supply 4and the other terminal of the resistor element R1. The negativeelectrode side of the constant voltage source 6 is connected (e.g.,grounded) to the reference plane of the potential in the power converter1A. This enables the constant voltage source 6 to bias the emitterterminal Te in each of the semiconductor elements 21 u, 21 v, 21 w at apredetermined constant voltage via the resistor element R1 and thenegative electrode side line Ln, and the U-phase main power supply inputterminal Tnu, the V-phase main power supply input terminal Tnv, and theW-phase main power supply input terminal Tnw, respectively.

As illustrated in FIG. 1 , the control device 3 provided in the powerconverter 1A is connected (for example, grounded) to the reference planeof the potential in the power converter 1A. The control device 3 isconfigured to output the input signals SinUH, SinVH, SinWH of a pulseshape, for example, to the gate drive circuit 22 and output the inputsignals SinUL, SinVL, SinWL of a pulse shape, for example, to the gatedrive circuit 23. This enables the control device 3 to control the gatedrive circuits 22, 23 and control the IGBT 201 provided in each of thesemiconductor elements 20 u, 20 v, 20 w and the IGBT 211 provided ineach of the semiconductor elements 21 u, 21 v, 21 w by, for example,pulse width modulation (PWM).

(Configuration and Operation of Detection Unit Provided in PowerConverter)

Next, the configuration and the operation of the U-phase detection unit234U, the V-phase detection unit 234V, and the W-phase detection unit234W provided in the power converter 1A according to this embodiment aredescribed using FIG. 2 and FIG. 3 with reference to FIG. 1 . The U-phasedetection unit 234U, the V-phase detection unit 234V, and the W-phasedetection unit 234W have similar configurations. Therefore, the U-phasedetection unit 234U, the V-phase detection unit 234V, and the W-phasedetection unit 234W are described below taking the W-phase detectionunit 234W as an example. For ease of understanding, FIG. 2 illustratesthe semiconductor element 21 w having the IGBT 211 as a temperaturelevel detection target by the W-phase detection unit 234W and a drivercircuit 231 driving the semiconductor element 21 w. Further, for ease ofunderstanding, FIG. 2 illustrates the U-phase detection unit 234U andthe V-phase detection unit 234V (specific circuit configurations are notillustrated) and terminals relating to the detection of the temperaturelevels of the IGBTs 211.

As illustrated in FIG. 2 , the gate drive circuit 23 has the drivercircuit 231 to which the input signal SinWL output from the controldevice 3 (see FIG. 1 ) is input and one terminal of a gate resistor 232arranged between the driver circuit 231 and the output terminal Tow ofthe gate drive circuit 23. The driver circuit 231 has a driver unit 231a connected to the input terminal Tiw of the gate drive circuit 23 and aconstant current source 231 b. An input terminal of the driver unit 231a is connected to the input terminal Tiw. An output terminal of thedriver unit 231 a is connected to the constant current source 231 b andthe gate resistor 232. The gate resistor 232 is provided to suppress avoltage fluctuation occurring in the switching operation of the IGBT 211provided in the semiconductor element 21 w. The driver unit 231 a isconfigured to output the gate signal SgVL of a high level when thevoltage level of the input terminal Tiw is low and the gate signal SgVLof a low level when the voltage level of the input terminal Tiw is high.

The constant current source 231 b outputs a predetermined gate currentto the gate terminal Tg of the semiconductor element 21 w via the gateresistor 232 and the output terminal Tow when the voltage level of theinput signal SinWL is low. Thus, the driver circuit 231 outputs the gatesignal SgWL with a high voltage level to the gate G of the IGBT 211provided in the semiconductor element 21 w via the gate resistor 232,the output terminal Tow, and the gate terminal Tg of the semiconductorelement 21 w. Therefore, the gate signal SgWL applied to the gate G ofthe IGBT 211 provided in the semiconductor element 21 w has a voltagelower by the voltage drop at the gate resistor 232 than the voltage ofthe gate signal SgWL output by the driver circuit 231.

On the other hand, when the voltage level of the input signal SinWL ishigh, the constant current source 231 b does not output the gate currentbut releases an electric charge charged to the gate capacitance (notillustrated) of the IGBT 211 provided in the semiconductor element 21 wto the reference potential terminal Tgnd. Thus, the driver circuit 231drives the IGBT 211 such that a voltage Vgw of the gate G of the IGBT211 provided in the semiconductor element 21 w is lowered to almost thesame level as the level of the voltage of the gate signal SgWL of a lowlevel.

As described above, the driver circuit 231 transits the state of theIGBT 211 provided in the semiconductor element 21 w from the off state(non-conduction state) to the on state (conduction state) (i.e., turnon) when the voltage level of the input signal SinWL input from theinput terminal Tiw is low. On the other hand, the driver circuit 231transits the state of the IGBT 211 provided in the semiconductor element21 w from the on state (conduction state) to the off state(non-conduction state) (i.e., turn off) when the voltage level of theinput signal SinWL input from the input terminal Tiw is high.

Although not illustrated, the gate drive circuit 23 has a driver circuithaving a configuration similar to the configuration of the drivercircuit 231 and driving the IGBT 211 provided in the semiconductorelement 21 u and a driver circuit having a configuration similar to theconfiguration of the driver circuit 231 and driving the IGBT 211provided in the semiconductor element 21 v. Although not illustrated,the gate drive circuit 23 has a gate resistor provided between thedriver circuit and the output terminal Tou and a gate resistor providedbetween the driver circuit and the output terminal Tov. The gate drivecircuit 22 (see FIG. 1 ) further has a driver circuit having aconfiguration similar to the configuration of the driver circuit 231 anddriving the IGBT 201 provided in each of the semiconductor elements 20u, 20 v, 20 w and a gate resistor provided between each of the drivercircuits and each of the output terminals Tou, Tov, Tow in each of thesemiconductor elements 20 u, 20 v, 20 w, respectively.

As illustrated in FIG. 2 , the gate drive circuit 23 has the W-phasedetection unit 234W detecting the temperature level of the IGBT 211based on the voltage of the gate G of the IGBT 211 provided in thesemiconductor element 21 w. Thus, the W-phase detection unit 234W isprovided in the gate drive circuit 23. In addition to the W-phasedetection unit 234W, the U-phase detection unit 234U and the V-phasedetection unit 234V are also provided in the gate drive circuit 23. Theformation of the U-phase detection unit 234U, the V-phase detection unit234V, and the W-phase detection unit 234W in a semiconductor chip onwhich the gate drive circuit 23 is formed enables downsizing of thepower converter 1A. The gate drive circuit 23 further has a voltagegeneration unit 233 generating a voltage for a comparison with thevoltage of the gate G of the IGBT 211 provided in the semiconductorelement 21 w.

The W-phase detection unit 234W has a comparator 234 a connected to thegate G of the IGBT 211 provided in the semiconductor element 21 w andthe voltage generation unit 233. The W-phase detection unit 234W furtherhas a logical product (AND) gate 234 b arithmetically operating thelogical product of a signal output from the comparator 234 a and theinput signal SinWL input from the input terminal Tiw.

The voltage generation unit 233 contains, for example, a constantvoltage source. The negative electrode side of the voltage generationunit 233 is connected to the reference potential terminal Tgnd providedin the gate drive circuit 23. The voltage generation unit 233 isconfigured to generate a comparison voltage Vref serving as thereference for the comparison in the comparator 234 a. The comparisonvoltage Vref is set such that an overheat threshold level that the IGBT211 provided in the semiconductor element 21 w can cope with isdetectable. The comparison voltage Vref is set to a voltage higher thana gate-emitter voltage Vge when the IGBT 211 provided in thesemiconductor element 21 w is operating within the range of the ratedtemperature.

The comparator 234 a is, for example, a hysteresis comparator containingan operational amplifier and a resistor element which is notillustrated. A non-inverting input terminal (+) of the comparator 234 ais connected to the other terminal of the gate resistor 232 and theoutput terminal Tow. The output terminal Tow is connected to the gate Gof the IGBT 211 via the gate terminal Tg of the semiconductor element 21w. Therefore, the non-inverting input terminal (+) of the comparator 234a is connected to the gate G of the IGBT 211 provided in thesemiconductor element 21 w. An inverting input terminal (−) of thecomparator 234 a is connected to the positive electrode side of thevoltage generation unit 233. An output terminal of the comparator 234 ais connected to a positive logic input terminal of the AND gate 234 b.

When the voltage Vgw of the gate G of the IGBT 211 provided in thesemiconductor element 21 w is equal to or smaller than the comparisonvoltage Vref generated by the voltage generation unit 233 (i.e., equalto or lower than the comparison voltage Vref), the comparator 234 aoutputs an output signal having a low voltage level to the AND gate 234b. When the voltage Vgw of the gate G of the IGBT 211 is higher than thecomparison voltage Vref, the comparator 234 a outputs an output signalhaving a high voltage level to the AND gate 234 b.

Herein, the principle of the temperature detection of the IGBT 211 inthe W-phase detection unit 234W is described using FIG. 2 and FIG. 3 .FIG. 3 is a diagram schematically illustrating the current-voltagecharacteristics of the IGBT 211. The horizontal axis of thecharacteristics illustrated in FIG. 3 represents a gate-emitter voltageVge (Unit: volt (V)) of the IGBT 211. The vertical axis of thecharacteristics illustrated in FIG. 3 represents a collector current Ic(Unit: ampere (A)) of the IGBT 211. “Vref” in FIG. 3 indicates thecomparison voltage Vref generated by the voltage generation unit 233.“Idv” in FIG. 3 indicates the collector current (collector-emittercurrent) flowing to the IGBT 211 after the transition to the on statewithin the range of the rated temperature. “IVn” in FIG. 3 indicates thecurrent-voltage characteristics of the IGBT 211 when operating withinthe range of the rated temperature. “IVh” in FIG. 3 indicates thecurrent-voltage characteristics of the IGBT 211 when operating at atemperature higher than the rated temperature.

When the voltage of the gate signal SgWL output by the driver circuit231 to switch on the IGBT 211 provided in the semiconductor element 21 wis defined as Vgo, the voltage drop at the gate resistor 232 is definedas V232, the voltage drop at the resistor element R1 is defined as Vr1,and the output voltage of the constant voltage source 6 is defined asV6, Equation (1) below is established between these voltages and thegate-emitter voltage Vge of the IGBT 211.Vgo=V232+Vge+Vr1+V6  (1)

When the voltage of the emitter E of the IGBT 211 provided in thesemiconductor element 21 w is defined as Vew and the voltage drop at thetemperature detection resistor element 213 provided in the semiconductorelement 21 w is defined as V213, the gate-emitter voltage Vge of theIGBT 211 in the on state can be represented by Equation (2) below.Vge=Vgw+V213−Vew  (2)

When the IGBT 211 is switched on, a gate current flowing from the gateterminal Tg of the semiconductor element 21 w partially flows to thetemperature detection resistor element 213, so that the voltage dropV213 occurs at the temperature detection resistor element 213.

In the temperature detection resistor element 213, the resistance valueincreases when the temperature becomes high, so that the voltage dropV213 increases. Therefore, as illustrated in Equation (2), thegate-emitter voltage Vge of the IGBT 211 increases when the temperaturebecomes high. More specifically, as illustrated in FIG. 3 , thecurrent-voltage characteristic IVh of the IGBT 211 when the temperatureis higher than the rated temperature is shifted to a side where thegate-emitter voltage Vge is higher relative to the current-voltagecharacteristic IVh of the IGBT 211 when the temperature is within therange of the rated temperature.

The voltage Vgo of the gate signal SgWL output by the driver circuit 231to switch on the IGBT 211 and the output voltage V6 of the constantvoltage source 6 are constant irrespective of the temperature of theIGBT 211. Therefore, when the temperature of the IGBT 211 becomes higherthan the rated temperature, the voltage drop V232 at the gate resistor232, the gate-emitter voltage Vge of the IGBT 211, and the magnitude ofthe voltage drop Vr1 at the resistor element R1 change (see Equation(1)). As described above, the gate-emitter voltage Vge of the IGBT 211increases when the temperature becomes high. Further, when thegate-emitter voltage Vge of the IGBT 211 increases, the collectorcurrent Ic flowing to the IGBT 211 increases, so that the voltage dropVr1 at the resistor element R1 increases. Therefore, when thetemperature of the IGBT 211 becomes higher than the rated temperature,the voltage drop V232 at the gate resistor 232 deceases. As a result,the voltage Vgw of the gate G of the IGBT 211 increases.

As illustrated in FIG. 3 , the comparison voltage Vref generated by thevoltage generation unit 233 is set to a voltage between the voltage Vgwof the gate G of the IGBT 211 when the gate-emitter voltage Vge of theIGBT 211 is a voltage Vge1 and the voltage Vgw of the gate G of the IGBT211 when the gate-emitter voltage Vge of the IGBT 211 is a voltage Vge2.The voltage Vge1 has a voltage value of the gate-emitter voltage Vgerequired to pass the collector current Ic of the current Idv to the IGBT211 within the range of the rated temperature. The voltage Vge2 has avoltage value of the gate-emitter voltage Vge where the collectorcurrent Ic starts to flow to the IGBT 211 at a temperature higher thanthe rated temperature.

When the comparison voltage Vref is set as described above, the voltageVgw of the gate G of the IGBT 211 is lower than the comparison voltageVref when the IGBT 211 performs the turn-on operation or maintains theon state within the range of the rated temperature (equal to or lowerthan the overheat threshold level). On the other hand, when the IGBT 211performs the turn-on operation or maintains the on state at atemperature higher than the rated temperature (a state where theoverheat threshold level is exceeded), the voltage Vgw of the gate G ofthe IGBT 211 is higher than the comparison voltage Vref. Therefore, whenthe IGBT 211 performs the turn-on operation or maintains the on statewithin the range of the rated temperature, a voltage input into thenon-inverting input terminal (+) of the comparator 234 a is lower than avoltage input into the inverting input terminal (−) of the comparator234 a, so that the comparator 234 a outputs an output signal having alow voltage level to the AND gate 234 b. On the other hand, when theIGBT 211 performs the turn-on operation or maintains the on state at atemperature higher than the rated temperature, a voltage input into thenon-inverting input terminal (+) of the comparator 234 a is higher thana voltage input into the inverting input terminal (−) of the comparator234 a, so that the comparator 234 a outputs an output signal having ahigh voltage level to the AND gate 234 b. As described above, theW-phase detection unit 234W is configured to detect the temperaturelevel of the relevant IGBT 211 based on the level (high or low) of thevoltage Vgw of the gate G of the IGBT 211 provided in the semiconductorelement 21 w with respect to the comparison voltage Vref input from thevoltage generation unit 233 (one example of the outside). As describedabove, the power converter 1A can detect the temperature level of theIGBT 211 using the voltage of the gate G of the IGBT 211, and thus doesnot need to be provided with a terminal for acquiring a reverse biasvoltage of the temperature detection resistor element 213. Thus, thepower converter 1A can prevent upsizing of the semiconductor elements 21u, 21 v, 21 w, the gate drive circuit 23, and the power converter 1Aitself.

As illustrated in FIG. 2 , the AND gate 234 b provided in the W-phasedetection unit 234W has the positive logic input terminal and a negativelogic input terminal. The positive logic input terminal of the AND gate234 b is connected to the output terminal of the comparator 234 a.Therefore, an output signal output from the comparator 234 a is inputinto the AND gate 234 b without the signal level being logicallyinverted. The negative logic input terminal of the AND gate 234 b isconnected to the input terminal Tiw of the gate drive circuit 23.Therefore, the input signal SinWL input from the input terminal Tiw isinput into the AND gate 234 b with the signal level being logicallyinverted.

When the IGBT 211 provided in the semiconductor element 21 w transitsfrom the off state to the on state or operates while maintaining the onstate within the range of the rated temperature, an output signal havinga low voltage level is input into the positive logic input terminal ofthe AND gate 234 b from the comparator 234 a. When the IGBT 211 providedin the semiconductor element 21 w transits from the off state to the onstate or operates while maintaining the on state at a temperature higherthan the rated temperature, an output signal having a high voltage levelis input into the positive logic input terminal of the AND gate 234 bfrom the comparator 234 a. On the other hand, when the IGBT 211 providedin the semiconductor element 21 w transits from the off state to the onstate or operates while maintaining the on state within the range of therated temperature, the voltage level of the input signal SinWL is low,and therefore the input signal SinWL of a high level is input into theAND gate 234 b from the negative logic input terminal.

Therefore, the AND gate 234 b outputs an output signal having a lowvoltage level when the IGBT 211 provided in the semiconductor element 21w transits from the off state to the on state or operates whilemaintaining the on state within the range of the rated temperature. Onthe other hand, the AND gate 234 b outputs an output signal having ahigh voltage level when the IGBT 211 provided in the semiconductorelement 21 w transits from the off state to the on state or operateswhile maintaining the on state at a temperature higher than the ratedtemperature. The W-phase detection unit 234W outputs the output signalof the AND gate 234 b as a detection signal for the temperature level ofthe IGBT 211 provided in the semiconductor element 21 w.

When the IGBT 211 provided in the semiconductor element 21 w transitsfrom the on state to the off state or maintains the off state, thevoltage level of the input signal SinWL input from the input terminalTiw is high. In this case, the input signal SinWL of a low level isinput into the AND gate 234 b from the negative logic input terminal.Therefore, when the IGBT 211 provided in the semiconductor element 21 wtransits from the on state to the off state or maintains the off state,the AND gate 234 b outputs a low level output signal irrespective of thevoltage level of the output signal output from the comparator 234 a.

Although a detailed description is omitted, the U-phase detection unit234U detecting the temperature level of the IGBT 211 provided in thesemiconductor element 21 u and the V-phase detection unit 234V detectingthe temperature level of the IGBT 211 provided in the semiconductorelement 21 v operate as with the W-phase detection unit 234W.

As illustrated in FIG. 2 , the gate drive circuit 23 has a logical sum(OR) gate 235 arranged between the output terminal of each of theU-phase detection unit 234U, the V-phase detection unit 234V, and theW-phase detection unit 234W and the detection signal output terminalTtp. One of three input terminals of the OR gate 235 is connected to theoutput terminal of the U-phase detection unit 234U. One of the remaininginput terminals of the OR gate 235 is connected to the output terminalof the V-phase detection unit 234V and the other one of the remaininginput terminals is connected to the output terminal of the W-phasedetection unit 234W. An output terminal of the OR gate 235 is connectedto the detection signal output terminal Ttp.

The OR gate 235 outputs a signal obtained by ORing the output signalsoutput from the U-phase detection unit 234U, the V-phase detection unit234V, and the W-phase detection unit 234W as the temperature detectionsignal Stemp.

When the IGBT 211 provided in each of the semiconductor elements 21 u,21 v, 21 w performs the turn-on operation or maintains the on statewithin the range of the rated temperature, output signals having a lowvoltage level are input into the OR gate 235 from the U-phase detectionunit 234U, the V-phase detection unit 234V, and the W-phase detectionunit 234W. In this case, the OR gate 235 outputs the temperaturedetection signal Stemp having a low voltage level to the control device3 (see FIG. 1 ).

On the other hand, when at least one of the IGBTs 211 provided in thesemiconductor elements 21 u, 21 v, 21 w performs the turn-on operationor maintains the on state at a temperature higher than the ratedtemperature, output signals having a high voltage level are input intothe OR gate 235 from the detection unit detecting the temperature levelof the at least one of the IGBTs 211 of the U-phase detection unit 234U,the V-phase detection unit 234V, and the W-phase detection unit 234W. Inthis case, the OR gate 235 outputs the temperature detection signalStemp having a high voltage level to the control device 3.

When the IGBT 211 provided in each of the semiconductor elements 21 u,21 v, 21 w performs the turn-off operation or is in the off state,output signals having a low voltage level are input into the OR gate 235from the U-phase detection unit 234U, the V-phase detection unit 234V,and the W-phase detection unit 234W. In this case, the OR gate 235outputs the temperature detection signal Stemp having a low voltagelevel to the control device 3 (see FIG. 1 ).

As described above, the gate drive circuit 23 can detect that any of theIGBTs 211 provided in the semiconductor elements 21 u, 21 v, 21 w has atemperature level higher than the temperature level of the ratedtemperature. When the voltage level of the temperature detection signalStemp input from the gate drive circuit 23 is high, the control device 3controls the gate drive circuits 22, 23 so as to stop the switchingoperation of the IGBT 201 provided in each of the semiconductor elements20 u, 20 v, 20 w and the IGBT 211 provided in each of the semiconductorelements 21 u, 21 v, 21 w. Thus, the overheat state of the IGBT 211 at atemperature level higher than the temperature level of the ratedtemperature among the IGBTs 211 provided in the semiconductor elements21 u, 21 v, 21 w is stopped. Therefore, the power converter 1A canprevent damage of the IGBT 211 at a temperature level higher than thetemperature level of the rated temperature and damage due to, forexample, an overcurrent in another IGBT 211 resulting from the damage ofthe IGBT 211.

(Effects of Power Converter)

The effects of the power converter according to this embodiment aredescribed using FIG. 4 and FIG. 5 with reference to FIG. 1 . FIG. 4 is adiagram illustrating an example of principal parts of a power converteras Comparative Example 1. FIG. 5 is a diagram illustrating an example ofprincipal parts of a power converter as Comparative Example 2.

As illustrated in FIG. 4 , a gate drive circuit 91 provided in a powerconverter 9A as Comparative Example 1 has a temperature detectioncircuit 911 and a temperature detection diode 912 connected to thetemperature detection circuit 911. The power converter 9A further has asemiconductor element 92 including an IGBT 921 driven by the gate drivecircuit 91. The semiconductor element 92 has a reflux diode 922connected in anti-parallel to the IGBT 921.

In the power converter 9A, the temperature detection diode 912 and theIGBT 921 are arranged apart from each other. Therefore, a thermalgradient of 10° C. or higher, for example, is generated between thetemperature detection diode 912 and the IGBT 921. Therefore, in thepower converter 9A, the temperature detection of the temperaturedetection diode 912 cannot follow a sudden temperature rise occurring inthe switching operation of the IGBT 921. Further, the temperaturedetection diode 912 cannot follow a temperature rise in the transitionof the switching operation of the IGBT 921. Therefore, the powerconverter 9A has a problem of damaging the IGBT 921 because thetemperature detection circuit 911 provided in the gate drive circuit 91cannot detect a sudden temperature rise or the like caused by the flowof an overcurrent to the IGBT 921.

On the other hand, the power converter 1A according to this embodimentincludes the semiconductor elements 21 u, 21 v, 21 w in which the IGBT211 and the temperature detection resistor element 213 are integratedinto one chip as illustrated in FIG. 1 . Therefore, the temperaturedetection resistor element 213 and the IGBT 211 are arranged close toeach other, so that the thermal gradient is hardly generated between thetemperature detection resistor element 213 and the IGBT 211. Thisenables the temperature detection resistor element 213 to detect thetemperature following the sudden temperature rise occurring in theswitching operation of the IGBT 211 and the temperature rise in thetransition of the switching operation of the IGBT 211. As a result, thepower converter 1A can prevent damage to the IGBTs 211 due to exceedingthe rated temperature.

As illustrated in FIG. 5 , a power converter 9B as Comparative Example 2has a gate drive circuit 93 having a temperature detection circuit 931and a semiconductor element 94 having an IGBT 941, a reflux diode 942,and a temperature detection diode 943. The IGBT 941, the reflux diode942, and the temperature detection diode 943 are integrated into onechip. The reflux diode 942 is connected in anti-parallel to the IGBT941.

The semiconductor element 94 has a terminal T9 a connected to an anodeof the temperature detection diode 943 and a terminal T9 b connected toa cathode of the temperature detection diode 943. The temperaturedetection diode 943 is connected to the temperature detection circuit931 provided in the gate drive circuit 93 via the terminals T9 a, T9 b.Therefore, the power converter 9B needs to be provided with theterminals T9 a, T9 b, and thus has a problem that the semiconductorelement 94 is upsized. Further, the power converter 9B needs to beprovided with terminals for connecting the temperature detection diode943 in the gate drive circuit 93, and thus has a problem that the numberof terminals in the gate drive circuit 93 increases.

On the other hand, in the power converter 1A, the temperature detectionresistor element 213 is arranged between the gate G and the emitter E ofthe IGBT 211 as illustrated in FIG. 1 . Therefore, in the powerconverter 1A, the semiconductor elements 21 u, 21 v, 21 w can beconnected to the gate drive circuit 23 by the gate terminals Tg withoutthe need for terminals for the temperature detection resistor elements213. This enables the power converter 1A to prevent upsizing of thesemiconductor elements 21 u, 21 v, 21 w and an increase in the number ofterminals of the gate drive circuit 22.

As described above, the power converter 1A according to this embodimentincludes the IGBTs 211 connected between the IGBTs 201 connected to thepositive electrode side of the variable power supply 4 and the negativeelectrode side of the variable power supply 4, the temperature detectionresistor elements 213 connected to the gates G to which the gate signalsSgUL, SgVL, SgWL for controlling the switching operations of the IGBTs211 are input and detecting the temperatures of the IGBTs 211, and theU-phase detection unit 234U, the V-phase detection unit 234V, and theW-phase detection unit 234W detecting the temperature levels of theIGBTs 211 based on the voltages of the gates G.

This enables the power converter 1A to prevent upsizing of chips onwhich the IGBTs 211 are formed and to detect the temperatures in theswitching operations of the IGBTs 211.

Second Embodiment

A power converter according to a second embodiment of the presentinvention is described using FIG. 6 . A power converter 1B according tothis embodiment has a feature that the configuration of a temperaturedetection unit detecting the temperature levels of the IGBTs isdifferent from the configuration of the power converter 1A according tothe above-described first embodiment. In the description of the powerconverter 1B according to this embodiment, constituent components havingthe same operations and functions as those of the constituent componentsof the power converter 1A according to the above-described firstembodiment are given with the same reference numerals and a descriptionthereof is omitted.

(Configuration of Power Converter)

The power converter 1B according to this embodiment has a configurationsimilar to the configuration of the power converter 1A according to theabove-described first embodiment except for a difference in theconfigurations of a U-phase detection unit, a V-phase detection unit,and a W-phase detection unit provided in a gate drive circuit.Therefore, the illustration of the overall configuration of the powerconverter 1B is omitted.

(Configuration and Operation of Detection Unit Provided in PowerConverter)

Next, the configuration and the operation of a temperature detectionunit provided in the power converter 1B according to this embodiment aredescribed using FIG. 6 with reference to FIG. 1 and FIG. 3 .

As illustrated in FIG. 6 , the power converter 1B includes the IGBTs 211connected between the IGBTs 201 (see FIG. 1 ) connected to the positiveelectrode side of the variable power supply 4 (see FIG. 1 ) and thenegative electrode side of the variable power supply 4, temperaturedetection resistor elements (one example of the temperature detectionelement) 213 connected to the gates G to which the gate signals SgUL,SgVL, SgWL for controlling the switching operations of the IGBTs 211 areinput and detecting the temperatures of the IGBTs 211, and a U-phasedetection unit 254U, a V-phase detection unit 254V, and a W-phasedetection unit 254W (all are examples of the detection unit) detectingthe temperature levels of the IGBTs 211 based on the voltages of thegates G.

The configuration and the operation of the U-phase detection unit 254U,the V-phase detection unit 254V, and the W-phase detection unit 254Wprovided in the power converter 1B are described using FIG. 6 withreference to FIG. 1 . The U-phase detection unit 254U, the V-phasedetection unit 254V, and the W-phase detection unit 254W have similarconfigurations. Therefore, the U-phase detection unit 254U, the V-phasedetection unit 254V, and the W-phase detection unit 254W are describedbelow taking the W-phase detection unit 254W as an example. For ease ofunderstanding, FIG. 6 illustrates the semiconductor elements 21 u, 21 v,21 w and a driver circuit 251 driving the semiconductor element 21 w.Further, for ease of understanding, FIG. 6 illustrates the U-phasedetection unit 254U and the V-phase detection unit 254V (specificcircuit configurations are not illustrated) and terminals relating tothe detection of the temperature levels of the IGBTs 211.

As illustrated in FIG. 6 , the gate drive circuit 23 has the drivercircuit 251 to which the input signal SinWL output from the controldevice 3 (see FIG. 1 ) is input and a gate resistor 252 arranged betweenthe driver circuit 251 and the output terminal Tow of the gate drivecircuit 23. The driver circuit 251 has a driver unit 251 a connected tothe input terminal Tiw of the gate drive circuit 23 and a constantcurrent source 251 b. An input terminal of the driver unit 251 a isconnected to the input terminal Tiw and an output terminal of the driverunit 251 a is connected to the constant current source 251 b and oneterminal of the gate resistor 252. The gate resistor 252 is provided tosuppress a voltage fluctuation occurring in the switching operation ofthe IGBT 211 provided in the semiconductor element 21 w. The driver unit251 a is configured to output the gate signal SgVL of a high level whenthe voltage level of the input terminal Tiw is low and output the gatesignal SgVL of a low level when the voltage level of the input terminalTiw is high.

When the IGBT 211 provided in the semiconductor element 21 w istransited from the off state to the on state, the constant currentsource 251 b outputs a predetermined gate current to the gate terminalTg of the semiconductor element 21 w via the gate resistor 252 and theoutput terminal Tow. Thus, the driver circuit 251 outputs the gatesignal SgWL having a high voltage level to the gate G of the IGBT 211provided in the semiconductor element 21 w via the gate resistor 252,the output terminal Tow, and the gate terminal Tg of the semiconductorelement 21 w. Therefore, the gate signal SgWL applied to the gate G ofthe IGBT 211 provided in the semiconductor element 21 w has a voltagelower by the voltage drop at the gate resistor 252 than the voltage ofthe gate signal SgWL output by the driver circuit 251.

On the other hand, when the IGBT 211 provided in the semiconductorelement 21 w is transited from the on state to the off state, theconstant current source 251 b does not output the gate current butreleases an electric charge charged to the gate capacitance (notillustrated) of the IGBT 211 provided in the semiconductor element 21 wto the reference potential terminal Tgnd. Thus, the driver circuit 251drives the IGBT 211 such that the voltage Vgw of the gate G of the IGBT211 provided in the semiconductor element 21 w is lowered to almost thesame level as the level of the voltage of the gate signal SgWL of a lowlevel.

As described above, the driver circuit 251 transits the state of theIGBT 211 provided in the semiconductor element 21 w from the off state(non-conduction state) to the on state (conduction state) (i.e., turnon) when the voltage level of the input signal SinWL input from theinput terminal Tiw is low. On the other hand, the driver circuit 251transits the state of the IGBT 211 provided in the semiconductor element21 w from the on state (conduction state) to the off state(non-conduction state) (i.e., turn off) when the voltage level of theinput signal SinWL input from the input terminal Tiw is high.

Although not illustrated, the gate drive circuit 23 has a driver circuithaving a configuration similar to the configuration of the drivercircuit 251 and driving the IGBT 211 provided in the semiconductorelement 21 u and a driver circuit having a configuration similar to theconfiguration of the driver circuit 251 and driving the IGBT 211provided in the semiconductor element 21 v. Although not illustrated,the gate drive circuit 23 has a gate resistor provided between thedriver circuit and the output terminal Tou and a gate resistor providedbetween the driver circuit and the output terminal Tov. The gate drivecircuit 22 (see FIG. 1 ) further has a driver circuit having aconfiguration similar to the configuration of the driver circuit 251 anddriving the IGBT 201 provided in each of the semiconductor elements 20u, 20 v, 20 w and a gate resistor provided between each of the drivercircuits and each of the output terminals Tou, Tov, Tow in each of thesemiconductor elements 20 u, 20 v, 20 w, respectively.

As illustrated in FIG. 6 , the gate drive circuit 23 has the W-phasedetection unit 254W detecting the temperature level of the IGBT 211based on the voltage of the gate G of the IGBT 211 provided in thesemiconductor element 21 w. Thus, the W-phase detection unit 254W isprovided in the gate drive circuit 23. In addition to the W-phasedetection unit 254W, the U-phase detection unit 254U and the V-phasedetection unit 254V are also provided in the gate drive circuit 23. Theformation of the U-phase detection unit 254U, the V-phase detection unit254V, and the W-phase detection unit 254W in a semiconductor chip onwhich the gate drive circuit 23 is formed enables downsizing of thepower converter 1B. The gate drive circuit 23 further has a voltagegeneration unit 253 generating a voltage for a comparison with thevoltage of the gate G of the IGBT 211 provided in the semiconductorelement 21 w.

The W-phase detection unit 254W has a comparator 254 a connected to thegate G of the IGBT 211 provided in the semiconductor element 21 w andthe voltage generation unit 253.

The voltage generation unit 253 contains, for example, a constantvoltage source. The negative electrode side of the voltage generationunit 253 is connected to the reference potential terminal Tgnd providedin the gate drive circuit 23. The voltage generation unit 253 isconfigured to generate a comparison voltage Vref serving as thereference for the comparison in the comparator 254 a. The comparisonvoltage Vref is set such that an overheat threshold level that the IGBT211 provided in the semiconductor element 21 w can cope with isdetectable. For example, the comparison voltage Vref is set to a voltagehigher than the gate-emitter voltage Vge when the IGBT 211 provided inthe semiconductor element 21 w is operating within the range of therated temperature.

The comparator 254 a has a configuration similar to the configuration ofthe comparator 234 a (see FIG. 2 ) in the above-described firstembodiment, for example. A non-inverting input terminal (+) of thecomparator 254 a is connected to the other terminal of the gate resistor252 and the output terminal Tow. The output terminal Tow is connected tothe gate G of the IGBT 211 via the gate terminal Tg of the semiconductorelement 21 w. Therefore, the non-inverting input terminal (+) of thecomparator 254 a is connected to the gate G of the IGBT 211 provided inthe semiconductor element 21 w. An inverting input terminal (−) of thecomparator 254 a is connected to the positive electrode side of thevoltage generation unit 253. An output terminal of the comparator 254 ais connected to an input terminal of a logical sum (OR) gate 255(details are described later).

When the voltage Vgw of the gate G of the IGBT 211 provided in thesemiconductor element 21 w is equal to or smaller than the comparisonvoltage Vref generated by the voltage generation unit 253 (i.e., equalto or lower than the comparison voltage Vref), the comparator 254 aoutputs an output signal having a low voltage level as a detectionsignal for the temperature level of the IGBT 211 provided in thesemiconductor element 21 w to the OR gate 255. When the voltage Vgw ofthe gate G of the IGBT 211 is higher than the comparison voltage Vref,the comparator 254 a outputs an output signal having a high voltagelevel as a detection signal for the temperature level of the IGBT 211provided in the semiconductor element 21 w to the OR gate 255.

The principle of the temperature detection of the IGBTs 211 in theU-phase detection unit 254U, the V-phase detection unit 254V, and theW-phase detection unit 254W is similar to the principle of thetemperature detection in the U-phase detection unit 234U, the V-phasedetection unit 234V, and the W-phase detection unit 234W in theabove-described first embodiment, and therefore a description isomitted.

As illustrated in FIG. 6 , the gate drive circuit 23 has the OR gate 255arranged between the output terminal of each of the U-phase detectionunit 254U, the V-phase detection unit 254V, and the W-phase detectionunit 254W and the detection signal output terminal Ttp. One of threeinput terminals of the OR gate 255 is connected to the output terminalof the U-phase detection unit 254U. One of the remaining input terminalsof the OR gate 255 is connected to the output terminal of the V-phasedetection unit 254V and the other one of the remaining input terminalsis connected to the output terminal of the W-phase detection unit 254W.An output terminal of the OR gate 255 is connected to the detectionsignal output terminal Ttp.

The OR gate 255 outputs a signal obtained by ORing the output signalsoutput from the U-phase detection unit 254U, the V-phase detection unit254V, and the W-phase detection unit 254W as the temperature detectionsignal Stemp.

When the IGBT 211 provided in each of the semiconductor elements 21 u,21 v, 21 w performs the turn-on operation or maintains the on statewithin the range of the rated temperature, output signals having a lowvoltage level are input into the OR gate 255 from the U-phase detectionunit 254U, the V-phase detection unit 254V, and the W-phase detectionunit 254W. In this case, the OR gate 255 outputs the temperaturedetection signal Stemp having a low voltage level to the control device3 (see FIG. 1 ).

On the other hand, when at least one of the IGBTs 211 provided in thesemiconductor elements 21 u, 21 v, 21 w performs the turn-on operationor maintains the on state at a temperature higher than the ratedtemperature, output signals having a high voltage level are input intothe OR gate 255 from the detection unit detecting the temperature levelof the at least one of the IGBTs 211 of the U-phase detection unit 254U,the V-phase detection unit 254V, and the W-phase detection unit 254W. Inthis case, the OR gate 255 outputs the temperature detection signalStemp having a high voltage level to the control device 3.

When the IGBT 211 provided in each of the semiconductor elements 21 u,21 v, 21 w performs the turn-off operation or is in the off state,output signals having a low voltage level are input into the OR gate 255from the U-phase detection unit 254U, the V-phase detection unit 254V,and the W-phase detection unit 254W. In this case, the OR gate 255outputs the temperature detection signal Stemp having a low voltagelevel to the control device 3 (see FIG. 1 ).

As described above, the gate drive circuit 23 in this embodiment candetect that any of the IGBTs 211 provided in the semiconductor elements21 u, 21 v, 21 w has a temperature level higher than the temperaturelevel of the rated temperature as with the gate drive circuit 23 in theabove-described first embodiment. This enables the control device 3 inthis embodiment to control the gate drive circuits 22, 23 as with thecontrol device 3 in the above-described first embodiment, and thereforethe overheat state of the IGBT 211 at a temperature level higher thanthe temperature level of the rated temperature is stopped. Therefore,the power converter 1B can prevent damage of the IGBT 211 at atemperature level higher than the temperature level of the ratedtemperature and damage due to, for example, an overcurrent in anotherIGBT 211 resulting from the damage of the IGBT 211.

As described above, the temperature detection resistor element 213provided in the power converter 1B according to this embodiment exhibitsa temperature detection function similar to that of the temperaturedetection resistor element 213 provided in the power converter 1Aaccording to the above-described first embodiment in accordance with thetemperature levels of the IGBTs 211. Further, the U-phase detection unit254U, the V-phase detection unit 254V, and the W-phase detection unit254W provided in the power converter 1B according to this embodimentexhibit a temperature detection function similar to that of the U-phasedetection unit 234U, the V-phase detection unit 234V, and the W-phasedetection unit 234W provided in the power converter 1A according to theabove-described first embodiment in accordance with the temperaturelevels of the IGBTs 211. Therefore, the power converter 1B according tothis embodiment obtains effects similar to the effects of the powerconverter 1A according to the above-described first embodiment.

The present invention is not limited to the embodiments described aboveand can be variously modified.

Although the power converters 1A, 1B according to the first embodimentand the second embodiment, respectively, described above have the IGBTs201 as the first switching element and the IGBTs 211 as the secondswitching element, the present invention is not limited thereto. Thepower converters 1A, 1B may include either a bipolar transistor or a MOStransistor in place of the IGBT as the first switching element and thesecond switching element. The first switching element and the secondswitching element may be wide bandgap semiconductor elements containingSiC, GaN, diamond, gallium nitride-based materials, gallium oxide-basedmaterials, AlN, AlGaN, ZnO, and the like.

In the first embodiment and the second embodiment described above, thesemiconductor elements 20 u, 20 v, 20 w constituting the upper arm partare driven by one gate drive circuit 22, but the present invention isnot limited thereto. The power converters 1A, 1B may be configured tohave three gate drive circuits and individually drive the semiconductorelements 20 u, 20 v, 20 w constituting the upper arm part by these gatedrive circuits.

The power converter 1A according to the above-described first embodimentmay have the driver circuit 251 and the U-phase detection unit 254U, theV-phase detection unit 254V, and the W-phase detection unit 254W in theabove-described second embodiment in place of the driver circuit 231 andthe U-phase detection unit 234U, the V-phase detection unit 234V, andthe W-phase detection unit 234W. The power converter 1B according to theabove-described second embodiment may have the driver circuit 231 andthe U-phase detection unit 234U, the V-phase detection unit 234V, andthe W-phase detection unit 234W in the above-described first embodimentin place of the driver circuit 251 and the U-phase detection unit 254U,the V-phase detection unit 254V, and the W-phase detection unit 254W.

The technical scope of the present invention is not limited to theillustrated, described, and exemplified embodiments, and includes allembodiments that bring about the equivalent effects to the intendedeffects of the present invention. Moreover, the technical scope of thepresent invention is not limited to the combination of the features ofthe inventions set forth in appended claims, but can be defined by alldesired combinations of particular features among all disclosedfeatures.

REFERENCE SIGNS LIST

-   -   1A, 1B power converter    -   2 inverter device    -   2U U-phase output arm    -   2V V-phase output arm    -   2W W-phase output arm    -   3 control device    -   4 variable power supply    -   5 smoothing capacitor    -   6 constant voltage source    -   7 motor    -   20 u, 20 v, 20 w, 21 u, 21 v, 21 w semiconductor element    -   22, 23 gate drive circuit    -   201 insulated gate bipolar transistor (IGBT)    -   202, 212 reflux diode    -   211 insulated gate bipolar transistor (IGBT)    -   213 temperature detection resistor element    -   231, 251 driver circuit    -   231 a, 251 a driver unit    -   231 b, 251 b constant current source    -   232, 252 gate resistor    -   233, 253 voltage generation unit    -   234 a, 254 a comparator    -   234 b AND gate    -   234U, 254U U-phase detection unit    -   234V, 254V V-phase detection unit    -   234W, 254W W-phase detection unit    -   235, 255 OR gate    -   C collector    -   Cu capacitor    -   D diode    -   E emitter    -   G gate    -   Ln negative electrode side line    -   Lp positive electrode side line    -   R1, R2, R3 resistor element    -   SgUH, SgUL, SgVH, SgVL, SgWH, SgWL gate signal    -   SinUH, SinUL, SinVH, SinVL, SinWH, SinWL input signal    -   Stemp temperature detection signal    -   TBu U-phase power supply terminal    -   Tc collector terminal    -   Tcc, Tdu power supply terminal    -   TccH, TccL control power supply terminal    -   Tcom common reference potential terminal    -   Te emitter terminal    -   Tg gate terminal    -   Tgnd reference potential terminal    -   TIS overcurrent detection input terminal    -   Tiu, Tiv, Tiw input terminal    -   Tiuh, Tiul, Tivh, Tivl, Tiwh, Tiwl signal input terminal    -   Tnu U-phase main power supply input terminal    -   Tnv V-phase main power supply input terminal    -   Tnw W-phase main power supply input terminal    -   Tou, Tov, Tow output terminal    -   Tp main power supply input terminal    -   Ts detection terminal    -   Tsu, Tsv, Tsw low potential terminal    -   Ttemp temperature output terminal    -   Ttp detection signal output terminal    -   TU U-phase output terminal    -   TV V-phase output terminal    -   TW W-phase output terminal

What is claimed is:
 1. A power converter comprising: a second switchingelement connected between a first switching element connected to apositive electrode side of a power supply and a negative electrode sideof the power supply; a temperature detection element connected to acontrol signal input terminal to which a control signal for controllinga switching operation of the second switching element is input andconfigured to detect a temperature of the second switching element; anda detection unit configured to detect a temperature level of the secondswitching element based on a voltage of the control signal inputterminal, wherein the detection unit is configured to detect thetemperature level based on a level of the voltage of the control signalinput terminal with respect to a comparison voltage input from anoutside.
 2. The power converter according to claim 1, wherein the secondswitching element and the temperature detection element are formed on asame semiconductor chip.
 3. The power converter according to claim 2,wherein the second switching element is an insulated gate bipolartransistor having a gate as the control signal input terminal.
 4. Thepower converter according to claim 2 comprising: a drive circuitconfigured to output the control signal to the control signal inputterminal and drive the second switching element, wherein the detectionunit is provided in the drive circuit.
 5. The power converter accordingto claim 1, wherein the second switching element is an insulated gatebipolar transistor having a gate as the control signal input terminal.6. The power converter according to claim 5, wherein the temperaturedetection element is a resistor element having one terminal connected tothe gate and another terminal connected to an emitter of the insulatedgate bipolar transistor.
 7. The power converter according to claim 6comprising: a drive circuit configured to output the control signal tothe control signal input terminal and drive the second switchingelement, wherein the detection unit is provided in the drive circuit. 8.The power converter according to claim 5 comprising: a drive circuitconfigured to output the control signal to the control signal inputterminal and drive the second switching element, wherein the detectionunit is provided in the drive circuit.
 9. The power converter accordingto claim 1 comprising: a drive circuit configured to output the controlsignal to the control signal input terminal and drive the secondswitching element, wherein the detection unit is provided in the drivecircuit.